A wide bandpass x-ray polarizer for photon energies near 8358 eV(LIIIabsorption edge of erbium) has been grown using molecular beam epitaxy. The results illustrate a general approach to preparing graded-lattice diffracting optical components. The active optical element is an 8-&mgr;m-thick single crystal film ofIn0.51Ga0.49Sbgrown on a GaAs (001) substrate. The alloy was chosen to ensure maximum linear polarization for the (006) Bragg reflection at the target energy. The polarizer reflectivity has a full width at half-maximum of 27 eV in a fixed geometry with an angle of 90° between the incident and diffracted beams. ©1997 American Institute of Physics.